Continuity mistake: When they jump in the pool, they drop the guitar. When they jump out their guitar is no longer in the pool.
Other mistake: When Captain Underpants falls in the Turbo Toilet 2000's mouth which has a liquid in it, he doesn't turn into Mr. Krupp.
Continuity mistake: When Ray starts to levitate in John's house, he looks down and he is hovering right above the table with the couch to his right. In the next shot, the table has suddenly vanished and it's now showing that the wall across from the couch with the TV and chair are on his right. (00:20:25)Quantom X
Continuity mistake: When Mariah is talking to the girls on the bridge at the beginning of the movie, the girl in green is holding her leash (her dog's that is) with her right hand in the shots from behind, the left hand in others including the wider ones from the protagonist's height. (00:02:25)Sammo